Colloquium: Christy B. Till
Christy B. Till
Mendenhall Postdoctoral Fellow, USGS, Menlo Park
Abstract: The compositions of primitive magmas provide the principal evidence for interpreting the depth, temperature and style of melt generation in planetary interiors. In this talk, I present a new experimentally-derived melting model for the Earth’s upper mantle and explore the effects of variations in mantle composition, pressure, temperature, and H2O content on melt composition. The model can be used to calculate the temperature and pressure at which primary basaltic magmas were produced in the mantle, as well as to model both near-fractional adiabatic decompression and batch melting. For example, this model is well suited to examine the temperature and pressure of origin for Quaternary basaltic lavas from southern Oregon and northern California. The model results along with recent geophysical observations are used to place constraints on the thickness of the mechanical lithosphere and determine the tectono-magmatic driving forces for Quaternary volcanism in these regions.